The present invention relates to a resin composition of propylene-ethylene random copolymer, more specifically a resin composition of propylene-ethylene random copolymer excellent in transparency, heat resistance and mechanical strength, and suitable for producing food containers, medical wares, laboratory wares, etc.
Polypropylene resin has been widely used as the material for injection molding, film production, sheet production, blow molding, etc. because polypropylene resin has relatively good heat resistance, chemical resistance and stiffness, and has good electrical properties and workability. A propylene-ethylene random copolymer produced from propylene and a small amount of ethylene further has a high impact strength and a good transparency in addition to the above properties of polypropylene resin. However, the transparency of propylene-ethylene random copolymer is still insufficient to apply it to food containers, medical wares, laboratory wares, etc., thereby limiting the use of propylene-ethylene random copolymer.
To improve on the transparency, it has been proposed to add to a polypropylene-type resin composition a nucleating agent such as a metal salt of carboxylic acid, a metal salt of aromatic sulfonic acid, a metal salt of aromatic phosphoric acid, a sorbitol compound (JP-A-58-25341 and JP-A-56-30449). Among these nucleating agents, the sorbitol derivative has been known most effective for improving the transparency. However, the sorbitol compound involves problems of low heat resistance and stiffness as well as offensive odor, bleedout, etc. Therefore, it has been expected that the polypropylene-type resin composition could be widely applied to various fields if such problems are solved.